MicroRNAs (miRNAs) play important roles in a wide range of biological processes,and their aberrant expressions are associated with various diseases.Here,we develop a label-free sensor for sensitive detection of microRNA on the basis of bioluminescence monitoring the released AMP from the target-triggered hybridization chain reaction-mediated ligation.The introduction of hybridization chain reaction (HCR) not only improves the sensitivity of microRNA assay,but also facilitates the sensitive detection of microRNA by designing specific hairpin probes,Moreover,this bioluminescence assay employs the target-dependent ATP as the reporter without the requirement for complicated immobilization,and separation steps.This highly sensitive and specific assay has potential to become a promising miRNA quantification method in biomedical research and clinical diagnosis.